KCSAN: data-race in __mod_timer / timer_clear_idle

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4fa640dc Merge tag 'vfio-v5.8-rc7' of git://github.com/awi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13737758900000
kernel config: https://syzkaller.appspot.com/x/.config?x=f1297bd8e780a21f
dashboard link: https://syzkaller.appspot.com/bug?extid=645659910ad2e8adc671
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [fwei...@gmail.com linux-...@vger.kernel.org mi...@kernel.org tg...@linutronix.de]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+645659...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __mod_timer / timer_clear_idle

write to 0xffff88812c11cb24 of 1 bytes by task 0 on cpu 1:
timer_clear_idle+0x2e/0x40 kernel/time/timer.c:1686
tick_nohz_restart_sched_tick kernel/time/tick-sched.c:860 [inline]
__tick_nohz_idle_restart_tick+0x20/0x190 kernel/time/tick-sched.c:1161
tick_nohz_idle_exit+0x13c/0x290 kernel/time/tick-sched.c:1202
do_idle+0x2c5/0x310 kernel/sched/idle.c:289
cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:372
start_secondary+0xe3/0x110 arch/x86/kernel/smpboot.c:268
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

read to 0xffff88812c11cb24 of 1 bytes by task 27863 on cpu 0:
forward_timer_base kernel/time/timer.c:899 [inline]
__mod_timer+0xa5b/0x1020 kernel/time/timer.c:1020
add_timer+0x38/0x50 kernel/time/timer.c:1147
__queue_delayed_work+0xea/0x150 kernel/workqueue.c:1649
queue_delayed_work_on+0x8d/0xe0 kernel/workqueue.c:1674
queue_delayed_work include/linux/workqueue.h:522 [inline]
batadv_nc_start_timer net/batman-adv/network-coding.c:79 [inline]
batadv_nc_worker+0x9f1/0xa00 net/batman-adv/network-coding.c:740
process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
kthread+0x20d/0x230 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 27863 Comm: kworker/u4:6 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.